MMP2 and neoplasm: CPT was linked with a hydrophilic tumor-penetrating peptide iRGD (a tumor-penetrating peptide that can bind to neuropilin-1 (NRP-1) and trigger tumor tissue penetration) through an MMP2 response connector (plglg peptide) and a reducible disulfide-ethyl carbonate (etcSS) connector to form supramolecular nanotubes (P-NTs) in water.